The generally invention relates to internal combustion engines and, more particularly, to a piston driven rotary-type internal combustion engine.
Engine designers are constantly endeavoring to design engines that maximize fuel efficiency while minimizing polluting byproducts of the combustion process. Fuel consumption has both a direct effect on the output of pollutants and the expense for the fuel used. Moreover, increasing the fuel efficiency of machinery using non-renewable resources, such as gasoline derived from oil, is an important social value. Minimizing pollutants minimizes the injurious effects on the environment and benefits the health of society on a global scale.
There have been many attempts to attain efficiency increases while minimizing pollutants. The rotary engine is one example of such attempts. The principal characteristics of conventional rotary internal combustion engines are well known in the field of art. Generally, a rotary engine uses the pressure of combustion to move a triangular rotor within an epitrochoidal-shaped rotor housing. The four cycles of conventional combustionxe2x80x94intake, compression, combustion and exhaustxe2x80x94each take place in its own portion of the housing. These cycles cause the rotor to rotate an eccentric output shaft geared to the rotor. The rotary engine seemingly would have increased efficiency due to the decrease of moving parts, a combustion event of 270xc2x0 of the output shaft rotation on every rotation, and better balance, since the rotor and shaft move in the same direction.
Despite these advantages, the conventional rotary engine has found little commercial success because the long and shallow shape of the combustion chamber hurts both emissions and fuel economy performance with respect to conventional piston engines. The relatively brief time period of the power stroke of the piston on the power portion of the rotary motion does not allow for complete combustion of the fuel. This leads to the exhaust of unburned hydrocarbons that must be cleaned up by a catalytic converter.
Known rotary engines, though capable of producing relatively high power output for their weight and size, have generally been too complex and, in operation, have exhibited excessively high wear, short useful life and relatively high fuel consumption. In operation, they generally produce undesirably high nitric oxide and unburned or partially burned hydrocarbon outputs. All of these add to problems of air pollution. Thus, the efficiency and emissions goals are not satisfied.
Another attempt to meet the efficiency and emissions goals is through the use of diesel cycle engines. The diesel cycle uses compression of a fuel and air mixture to ignite a combustion event, rather than a spark. This allows the diesel engine to utilize direct injection of the fuel and a higher compression ratio than ordinary gasoline. The higher compression ratio results in better efficiency than for ordinary gasoline engines. Moreover, diesel fuel has a higher energy density than gasoline. The combination of greater energy density and higher compression results in much-improved fuel efficiency.
However, diesel cycle engines perform poorly in emissions performance. The combustion in a diesel engine produces significant amounts of polluting nitrogen oxides NOX). This is especially true in large-scale uses, such as ship engines, or as power sources for electric generation plants. These NOX have been addressed primarily through the use of selective catalytic reduction of the nitrogen oxides. Catalytic converter use at large-scale diesel engines, such as ships and power plants, is not always feasible due to costs and space concerns. Therefore, elimination of the formation of NOX in the combustion chamber has been a focus of technological development.
One measure to reduce NOX in diesel engines is through the injection of water into the combustion chamber to reduce the combustion temperature. The goal is to reduce the peak temperature arising at the flame, which results in a reduction in NOX formation. Forming fewer NOX equals fewer NOX emissions from the engine. Typically, the water is injected into the combustion chamber shortly before combustion, during combustion, or is mixed with the fuel before injection. A conventional four-stroke diesel engine usually injects the water towards the end of the compression stroke. The use of water injection on a piston-driven diesel engine addresses the emissions concerns to a certain degree. However, the use of a four-cycle reciprocating engine design still has the inherent efficiency drawbacks of producing only one 180xc2x0 power stroke for every other cycle of the piston.
Attempts have been made to design a diesel-fueled rotary engine. U.S. Pat. No. 3,957,021, to Loyd, discloses a rotary diesel engine. Said patent discusses the prior unsatisfactory attempts to utilize diesel fuel in rotary engines. The prior attempts produced unsatisfactory results due to the inability to create sufficient compression in the combustion chamber portion of the rotary housing. The Loyd patent addresses the compression problem by providing a precombustion chamber adjacent to the rotor housing and in communication with the housing.
A fuel injector is disposed in the chamber for injecting fuel into the supplied combustion air. The combustion air is provided, in part, by a compressor, which ensures a sufficient pressure is maintained to combust the diesel fuel. The introduction of fuel into the precombustion chamber in the presence of high pressure and temperature causes the combustion of the fuel to flash into the working chamber of the housing via an outlet port. The burning continues in the working chamber to cause the rotor to rotate the output shaft.
U.S. Pat. No. 6,125,813, to Louthan et al., discloses an alternate method of providing a precombustion chamber to a diesel fueled rotary engine without the need for a separate compressor. However, Louthan and Loyd do not address the emissions issues associated with triangular rotors or with the use of diesel fuel, as discussed previously. Therefore, there is a continuing need to provide an internal combustion engine with improved fuel economy and reduced emissions.
The positive displacement turbine solves many of the above-indicated problems of rotary engines by providing a rotary engine, which produces an exhaust low in air pollutants while operating efficiently and requiring minimal cooling.
The positive displacement turbine generally comprises a separate compressor, combustion chamber and expansion chamber. The expansion chamber utilizes a crescent-shaped piston, a hub and a cam track in order to extract maximum energy from expanding combustion gases. The positive displacement turbine may also utilize an internal coolant injector system. The coolant injector system assists in cooling the positive displacement turbine, improves efficiency by water injection, and injects a chemical exhaust precipitator into the combustion chamber to react with and precipitate pollutants from the exhaust stream, leaving only carbon dioxide and a few inert gases to escape into the atmosphere.
The positive displacement turbine is adaptable for use with many different fuels, including diesel fuel, gasoline and gaseous fuels including hydrogen. It is adaptable and scaleable for various-sized applications. The invention is also well-adapted to be manufactured from non-traditional engine materials such as composites and ceramics.